Method and apparatus for enabling cell reselection for wtru operating in discontinuous reception

ABSTRACT

A method for discontinuous reception (DRX) implemented in a wireless transmit/receive unit (WTRU) during cell reselection including initiating cell reselection; disabling DRX operation, wherein disabling DRX operation enables continuous reception; transmitting a CELL UPDATE message; receiving a CELL UPDATE CONFIRM message; and enabling DRX operation based on the received CELL UPDATE CONFIRM message.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/363,197, filed Jan. 30, 2009 which claims the benefit of U.S.Provisional Patent Appl. No. 61/025,657, filed Feb. 1, 2008, which isincorporated by reference as if fully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

Discontinuous Reception (DRX) and Discontinuous Transmission (DTX) wereintroduced in the CELL_DCH state as part of the Continuous PacketConnectivity (CPC) feature of the Third Generation Partnership Project(3GPP) Release 7. DRX and DTX operation, applied to wirelesstransmit/receive units (WTRUs) in the CELL_DCH state, allow the radioaccess network to maintain temporarily inactive WTRUs in the CELL_DCHstate by reducing the interference cause by these WTRUs (i.e. reducewasted system capacity) and reducing the WTRU battery consumption.

In Release 7, a two-tiered DRX scheme was introduced for WTRUs in theCEL L_PCH state. Upon transition to the CELL_PCH state the WTRU entersDRX mode using a shorter DRX cycle and after a period of inactivity theWTRU switches to a longer DRX cycle.

A new feature has been introduced as part of 3GPP Wideband Code DivisionMultiple Access (WCDMA) Release 8 to enable DRX operation for a WTRU inthe CELL_FACH state. A fixed DRX pattern was introduced which is inconstant use during the entire time period that a WTRU is in theCELL_FACH state with the exception of when the WTRU has enhancedDedicated Channel (E-DCH) resources allocated. When the WTRU isallocated E-DCH resources it may operate in continuous reception andtransmission mode, allowing it to continuously transmit and receivecontinuously on the downlink. After the E-DCH resources are released,the WTRU and a Node-B then start to follow the fixed DRX pattern derivedfrom a Radio Network Temporary Identifier (RNTI) of the WTRU.

The DRX pattern used by a specific WTRU may be determined by auser-specific identifier such as an E-DCH-RNTI (E-RNTI), High-SpeedDownlink Shared Channel (HS-DSCH) RNTI (H-RNTI), or Controlling RadioNetwork Controller (C-RNTI). The behavior of the WTRU and the DRXpattern is not specified for a WTRU that does not have an allocated RNTI(e.g. when the WTRU sends a CELL_UPDATE for cell reselection and has notyet received its CELL_UPDATE CONFIRM message). Additionally, WTRUbehavior is not defined for when a radio link failure occurs in theCELL_DCH state. A WTRU experiencing the radio link failure moves to theCELL_FACH state and deletes all the dedicated downlink and uplinkinformation allocated to the WTRU while in CELL_DCH. These resourcesinclude the E-RNTI, H-RNTI, and C-RNTI. The WTRU then sends a CELLUPDATE message with cause “radio link failure” and waits for the CELLUPDATE CONFIRM. During this time, the WTRU does not have a dedicatedRNTI. Further, no DRX behavior is defined for a WTRU in idle mode andinitiating a Radio Resource Control (RRC) connection request. When aWTRU is in idle mode, the WTRU may not have a dedicated RNTI when a RRCConnection Request message is sent. As a result, the WTRU has to wait toreceive a RRC Connection SETUP message from the network over HS-DSCH,which may assign a dedicated RNTI to the WTRU.

Similarly, methods for managing the transitions of a WTRU between DRXoperation and Continuous Reception (CRX) operation are desired. In oneproposal a WTRU may be configured to link the transition between DRXoperation and CRX operation to the start of an enhanced random accesschannel (E-RACH) access or an E-DCH in the CELL_FACH state and Idle modeprocedure. Further, the transition of a WTRU between CRX operation toDRX operation may be linked to the release of its allocated E-DCHresources. However, this behavior may create problems because a WTRU maybe operating in DRX in certain conditions where it would need to belistening for signaling or data from a UMTS Terrestrial Radio AccessNetwork (UTRAN). For example, such a scenario may occur when a WTRUsends a CELL_UPDATE message for cell reselection using the E-DCH in theCELL_FACH state to move to a new Node-B and then resumes DRX operationafter releasing its E-DCH resources. If the new Node-B is unaware of theDRX pattern used by the WTRU, it may transmit its response (e.g. theCELL_UPDATE CONFIRM) while the WTRU is in DRX, thus preventing the WTRUfrom receiving the response. Another scenario where a problem may occuris when a WTRU sends a CELL_UPDATE message for cell reselection usingthe Random Access Channel (RACH) to moves to a new Node-B. Since thestart of a RACH access procedure is not currently a trigger totransition from DRX to CRX, the new Node-B may transmit its response(e.g. the CELL_UPDATE CONFIRM) while the WTRU is in DRX, thus preventingthe WTRU from receiving the response.

Another problem may occur if the WTRU is allowed to autonomously releasethe E-DCH resources and the network does not receive an indication thatthe resources were released. In this scenario, the WTRU may be in DRXoperation while the network thinks the WTRU is still in CRX mode becausethe E-DCH resources are still allocated. This may result in the WTRUfailing to receive a message in the downlink.

SUMMARY

A method and apparatus for enabling cell reselection for WTRUs operatingin discontinuous reception mode are disclosed. A method fordiscontinuous reception (DRX) implemented in a wireless transmit/receiveunit (WTRU) during cell reselection including initiating cellreselection; disabling DRX operation, wherein disabling DRX operationenables continuous reception; transmitting a CELL UPDATE message;receiving a CELL UPDATE CONFIRM message; and enabling DRX operationbased on the received CELL UPDATE CONFIRM message.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 shows a wireless communication system including a plurality ofWTRUs , a Node-B , a controlling radio network controller (CRNC), aserving radio network controller (SRNC) , and a core network;

FIG. 2 is a functional block diagram of a WTRU and a Node-B of thewireless communication system of FIG. 2;

FIG. 3 shows an example realization of the DRX behavior;

FIG. 4 shows example realization of DRX behavior while performing cellreselection;

FIG. 5 shows example realization of DRX behavior when E-DCH in theCELL_FACH state and Idle mode is not supported; and

FIG. 6 shows an example DRX timing period for a WTRU during a RACHprocedure.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

When referred to hereafter, the term RNTI may refer to a dedicatedE-RNTI, H-RNTI, C-RNTI or any other dedicated identifier that isassigned by the UTRAN to the WTRU during an RRC connection.

When referred to hereafter, the term E-RACH may refer to a resource thatis used by a WTRU for uplink contention-based access in Evolved HighSpeed Packet Access (HSPA+) systems. The term E-RACH resource may alsoindicate any combination of a scrambling code, a channelization code, atimeslot, an access opportunity and/or a signature sequence that areassociated to uplink contention-based channel in a future systemarchitecture. The term E-RACH may also refer to the use of E-DCH inCELL_FACH, CELL_PCH, URA_PCH states or Idle mode.

FIG. 1 shows a wireless communication system 100 including a pluralityof WTRUs 110, a Node-B 120, a controlling radio network controller(CRNC) 130, a serving radio network controller (SRNC) 140, and a corenetwork 150. The Node-B 120 and the CRNC may be referred to as theUTRAN.

As shown in FIG. 1, the WTRUs 110 are in communication with the Node-B120, which is in communication with the CRNC 130 and the SRNC 140.Although three WTRUs 110, one Node-B 120, one CRNC 130, and one SRNC 140are shown in FIG. 1, it should be noted that any combination of wirelessand wired devices may be included in the wireless communication system100.

FIG. 2 is a functional block diagram 200 of a WTRU 110 and the Node-B120 of the wireless communication system 100 of FIG. 1. As shown in FIG.2, the WTRU 110 is in communication with the Node-B 120 and both areconfigured to perform a method of enabling cell reselection for a WTRUoperating in DRX mode.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 115, a receiver 116, a transmitter 117,and an antenna 118. The processor 115 is configured to perform a methodof enabling cell reselection for a WTRU operating in DRX mode. Thereceiver 116 and the transmitter 117 are in communication with theprocessor 115. The antenna 118 is in communication with both thereceiver 116 and the transmitter 117 to facilitate the transmission andreception of wireless data.

In addition to the components that may be found in a typical basestation, the Node-B 120 includes a processor 125, a receiver 126, atransmitter 127, and an antenna 128. The processor 125 is configured toperform a method of enabling cell reselection for a WTRU operating inDRX mode. The receiver 126 and the transmitter 127 are in communicationwith the processor 125. The antenna 128 is in communication with boththe receiver 126 and the transmitter 127 to facilitate the transmissionand reception of wireless data.

In a first embodiment, the WTRU 110 and the Node-B 120 may be configuredto disable DRX operation based on a trigger or combination of triggers.For example, the WTRU 110 may be configured to disable DRX operationduring cell selection/reselection when it releases its RNTI. The WTRU110 may further be configured to disable DRX operation during cellselection/reselection if it does not have an RNTI. During cellselection/reselection, the Node-B 120 may determine that no H-RNTIvariable is associated with the WTRU.

For example, while in CELL_FACH State, the WTRU 110 may be configured tocontinuously monitor the signal strength of neighboring cells. At somepoint, a change of “best cell” event may occur, where a neighboring cellmeets the criteria for the WTRU 110 to perform a cell reselection (thecriteria for cell reselection is well established as prior art). At thispoint, the WTRU may acquire system information (SI) in the new cellwhich is broadcast over the broadcast control channel (BCCH). The WTRUthen may reset lower layers (e.g. MAC) and clear all variables andconfiguration parameters related to the previous cell. The WTRU 110 mayfurther be configured to disable DRX operation. The WTRU 110 alsoconfigures lower layers for reception and transmission in the new cellusing the configuration parameters acquired in the new cell. Then theWTRU 110 may transmit a a CELL_UPDATE message in the new cell and waitsfor a CELL_UDPATE_CONFIRM from the UTRAN.

Additional triggers for disabling DRX operation may also be used. Forexample, the WTRU 110 may disable DRX operation whenever it triggers acell reselection. The WTRU 110 may disable DRX operation when sending aCELL_UPDATE using the E-DCH in the CELL_FACH state. The WTRU 110 may beconfigured to disable DRX operation when sending a CELL UPDATE messagefor cell reselection using the E-DCH in the CELL_FACH state. The WTRU110 may also disable DRX operation when sending a CELL UPDATE messagefor radio link failure using the E-DCH in the CELL_FACH state. The WTRU110 may disable DRX operation when sending a CELL UPDATE message usingthe RACH. The WTRU 110 may disable DRX operation when sending aCELL_UPDATE message for cell reselection using the RACH. The WTRU 110may also disable DRX operation when sending a CELL_UPDATE message forradio link failure using RACH or when an RRC Connection Request messageis sent. The WTRU 110 may be configured to disable DRX operation when itstarts reading the System Information (SI) that is broadcast over thebroadcast control channel (BCCH) and the WTRU 110 starts reception ofbroadcast and/or multicast data, (e.g. Multimedia Broadcast MulticastService (MBMS)).

The WTRU 110 and the Node-B 120 may also be configured to enable DRXoperation based on triggers. The WTRU 110 may be configured to enableDRX operation after receiving a dedicated RNTI (e.g. H-RNTI, E-RNTIand/or C-RNTI). The WTRU 110 may also enable DRX operation afterreceiving a CELL_UPDATE CONFIRM message from UTRAN. The WTRU 110 mayenable DRX operation upon receiving a CELL_UPDATE CONFIRM message fromUTRAN after having sent a CELL_UPDATE for cell reselection. The WTRU 110may also enable DRX operation upon receiving an RRC Connection Setupmessage from UTRAN. In another option the WTRU 110 may be configured toenable DRX operation upon completing a reading of System Informationthat is broadcast over the BCCH.

Optionally, the WTRU 110 may be configured to disable DRX operation fora pre-configured period of time, Tx, or for N transmission timeintervals (TTIs) after decoding a first High-Speed Shared ControlChannel (HS-SCCH) transmission with the WTRU's H-RNTI and/or aftersuccessfully receiving a first downlink MAC-ehs protocol data unit(PDU), where Tx or N may be configured by higher layers orpre-configured in the WTRU 110. The WTRU 110 may then receive downlinkdata continuously for a period of time known by the Node-B 120 and theWTRU 110. After the time expires the WTRU 110 may be configured toenable DRX operation and, if the network has additional data totransmit, the Node-B 120 may use a DRX listening period to send data tothe WTRU 110. Where listening periods define periods where the WTRU 110must be capable of receiving transmission on the downlink; the WTRU 110may turn off its receiver outside of these listening periods to savebattery power. The WTRU 110 may then again move to continuous receptionupon reception of HS-SCCH or first PDU after enabling DRX operation.

The triggering conditions listed herein to enable and disable DRXoperation may be combined with any other triggering conditions that arewell known by those skilled in the art such as activity/inactivity basedtimers, explicit signaling from UTRAN, etc.

In order for a WTRU 110 in DRX operation to properly perform a cellreselection (or alternatively cell update), the WTRU 110 must be capableof receiving the CELL_UPDATE CONFIRM message from the new Node-B.Accordingly, the WTRU 110 may be configured to disable DRX operationwhile performing cell reselection.

FIG. 3 is a flow diagram of a DRX operation (300) during cellreselection (or alternatively cell update). The WTRU 110 may beconfigured to operate in DRX mode (310). An event may occur signaling achange of best cell (i.e. cell reselection or cell update), (320). TheWTRU 110 may then disable DRX operation (330) (i.e. start continuousreception.) The WTRU 110 may then initiate a cell reselection/cellupdate procedure by transmitting a CELL UPDATE message (340). The WTRU110 remains in continuous reception until a CELL UPDATE CONFIRM messageand dedicated RNTI are received indicating the cell reselection/updatewas successful (350). If the procedure was successful, the WTRU 110enables DRX operation in the new cell (360). If the procedure wasunsuccessful, the WTRU 110 does not enable DRX operation (370) (e.g.maintain continuous reception or Idle mode.)

If a radio link failure occurs, the WTRU 110 may be configured totransmit a CELL UPDATE message indicating a radio link failure. Thismessage may be transmitted even while the WTRU 110 is in the CELL_FACHstate. The WTRU 110 may then disable DRX operation until the CELL UPDATECONFIRM MESSAGE is received. Upon receiving the CELL UPDATE CONFIRMMESSAGE, the WTRU 110 may enable DRX operation.

For example, if a WTRU 110 transitions from CELL_PCH to the CELL_FACHstate and does not have a dedicated H-RNTI when this transition occurs,the WTRU 110 may further be configured to disable DRX operation untilthe CELL UPDATE CONFIRM message is received and the WTRU 110 obtains adedicated RNTI. The WTRU 110 may further be configured to enable DRXoperation upon reception of CELL UPDATE CONFIRM if a dedicated RNTI isassigned and the WTRU 110 remains in the CELL_FACH state.

A WTRU 110 attempting to establish an RRC connection with the UTRAN maybe configured to disable DRX operation. For example, the WTRU 110 maydisable DRX operation in the CELL_FACH state when attempting to send anRRC Connection Request message from Idle Mode. The WTRU 110 may furtherbe configured to only enable DRX operation in the CELL_FACH state whenthe WTRU 110 receives an RRC Connection Setup message from the UTRAN.Alternatively, the WTRU 110 may enable DRX operation when it is assignedan RNTI by the UTRAN.

As part of the alternate embodiment, the WTRU 110 may be configured tocontinue DRX operation (if enabled) while performing cell reselection(or alternatively cell update procedure). The WTRU 110 may determine theDRX pattern to be used by selecting a common RNTI which maps to a commonDRX pattern. The common DRX pattern may be common to all WTRUs of acell. In this case, the DRX pattern (or its index) may be signaledthrough a common control channel such as a broadcast channel.

Alternatively, a common DRX pattern may be assigned for a group of WTRUsin a cell. This common DRX pattern may be linked to common HS-DSCHresources broadcast for the WTRUs. In this case, a WTRU 110 may beconfigured to receive a list of DRX patterns (or index) broadcast oversystem information blocks (SIBs). The WTRU 110 may then select one ofthe DRX pattern based on a formula known by both the UTRAN and the WTRU110, which uses the U-RNTI of the WTRU 110.

In another alternative, the WTRU 110 may be configured to base the DRXpattern on a common H-RNTI. The WTRU 110 may receive a CELL UPDATECONFIRM message. In response to receiving the CELL UPDATE CONFIRMmessage, the WTRU may switch to using the dedicated RNTI. The UTRAN maybe aware of the common H-RNTI the WTRU 110 is using and therefore theUTRAN may know the DRX pattern that the WTRU 110 is using.

In another alternative, the common DRX pattern may be common to allWTRUs of the system in which case, the WTRU 110 may be preconfiguredwith the DRX pattern (or its index). Alternatively, the WTRU 110 may beconfigured with the DRX pattern during RRC connection. Alternatively,the WTRU 110 may be configured to receive a signal configuring the DRXpattern, through a common control channel such as a broadcast channel.

In yet another alternative the common DRX pattern may be a fixed DRXpattern. The network may be configured to signal the fixed DRX patternto the WTRU 110 during RRC connection or during RRC reconfigurationmessages. The WTRU 110 may also be pre-configured with the fixed DRXpattern.

FIG. 4 is a flow diagram of a DRX operation (400) for a WTRU 110,wherein the WTRU 110 changes the DRX pattern from using a WTRU-specificDRX pattern to a common or fixed DRX pattern to while performing a cellreselection (or alternatively cell update). Initially, the WTRU 110 maybe configured with a dedicated DRX pattern while operating in theCELL_FACH state (410). A change of “best cell” event occurs (420). TheWTRU 110 then configures its DRX operation with a common DRX pattern(430). Once the cell reselection procedure (or cell update) is complete(440), the WTRU 110 may determine whether the procedure was successful(450). If the procedure was successful the WTRU 110 may be configured toresume DRX operation using a dedicated DRX pattern that may be based onan RNTI that has been assigned to the WTRU (460). If the procedure wasunsuccessful, the WTRU 110 does not enable DRX operation (470).

In a third embodiment, the WTRU 110 may be configured to continue usinga DRX pattern it was using prior to performing cell reselection until itreceives a CELL UPDATE CONFIRM.

In order for the target cell to successfully send the CELL UPDATECONFIRM to the new WTRU, it must know the DRX pattern the WTRU 110 isusing. Accordingly, the RNC may be configured to signal to the targetcell the RNTI that the WTRU 110 was using in the source cell. Thenetwork may then be configured to calculate the DRX pattern for the WTRU110 when sending the CELL UPDATE CONFIRM. Alternatively, the RNC may beconfigured to signal the DRX pattern that the WTRU 110 was using in thesource cell.

Alternatively, the WTRU 110 may be configured to remain in DRX operationduring cell reselection. The WTRU 110 may determine its DRX cycle andpattern based on its WTRU 110 U-RNTI. In this embodiment, the RNC maythen be configured to signal the U-RNTI to the target Node-B 120 whichmay then determine the WTRUs DRX pattern and send the CELL UPDATECONFIRM.

Alternatively, the WTRU 110 may be configured to always use the U-RNTIto derive the DRX pattern and thus it may remain in DRX operation evenduring cell reselection. The WTRU 110 may then be configured to changeits DRX pattern when the U-RNTI is changed.

The above described DRX operations may also be applied to the case wherethe WTRU 110 attempts to establish an RRC connection with the UTRAN. Inthis case, the WTRU 110 employs a common DRX pattern until it receivesthe RRC Connection Setup message from UTRAN.

In another embodiment, the WTRU 110 may be configured to autonomouslyrelease E-DCH resources. The WTRU 110 may enable DRX operation when theE-DCH resources are released. The E-DCH resources may be released ifE-DCH resource timer expires and the WTRU 110 has to release resourcesdue to timer expiration. Additionally, the E-DCH resources may bereleased due to explicit indication from the Node-B. The WTRU 110 mayfurther be configured to release the E-DCH resources if it no longer hasany data to transmit in the UL.

In some situations, the WTRU 110 may be configured to autonomouslyrelease the E-DCH resources without any of the aforementioned triggers.If the WTRU 110 releases the resources without any of the abovementionedtriggers, the WTRU 110 may be configured to enable DRX operation onlyafter the E-DCH release timer expires. In this embodiment, the WTRU 110may be configured to keep the timer running even if the E-DCH resourcesare released autonomously. The Node-B 120 may be configured to signal anexplicit release indication. When an explicit Node-B 120 releaseindication is received, the WTRU 110 may stop the timer and enable DRXoperation.

Optionally, the WTRU 110 may be configured to enable DRX operation modeonly after N DRX cycles, where N may be configured by upper layers orpreconfigured or calculated by the WTRU. The WTRU 110 may also beconfigured to enable DRX operation after a safe guard timer (Tg)expires, where Tg is started at the time the WTRU 110 releases theresources. The WTRU 110 may also be configured to enter DRX mode onlyafter receiving an acknowledgment from the Node-B 120 that the resourcesare known to be released. Such an acknowledgment may be transmittedthrough physical layer signaling (e.g. E-DCH Absolute Grant Channel(E-AGCH) with a specific value), Layer 2 (L2) signaling or RRCsignaling.

In another embodiment, the WTRU 110 or the UTRAN may not be configuredto use the E-DCH in the CELL_FACH state. In this embodiment, a mechanismcomprising disabling DRX operation upon initiation of the E-DCH in theCELL_FACH STATE and enabling DRX operation upon release of E-DCHresources may no longer applicable. Accordingly, the WTRU 110 may beconfigured to enable DRX operation even if the E-DCH in the CELL_FACHstate is not supported; therefore methods that allow the WTRU 110 toenable DRX operation without support for the E-DCH in the CELL_FACHstate are described in greater detail hereafter.

The DRX pattern may be based on the WTRU 110 RNTI such as C-RNTI,H-RNTI, U-RNTI or S-RNTI.

FIG. 5 shows an example of DRX operation when the E-DCH in the CELL_FACHstate is not supported. The WTRU 110 may be configured with DRXoperation enabled except when a RACH preamble is sent (510). While inDRX mode, the WTRU 110 determines whether there is uplink data totransmit (520). If there is uplink data to transmit, the WTRU 110 may beconfigured to transmit a RACH preamble (530). The WTRU 110 then disablesDRX operation (540). This may allow the WTRU 110 to successfully receivethe Acquisition Indicator Channel (AICH) sent by the Node-B. The DRXoperation may remain disabled until an AICH response is received (550).If no AICH transmission is received for a predetermined time period, DRXoperation remains disabled and the WTRU 110 performs a power ramp up tosend another preamble (560). If an ACK is received on the AICH, the WTRU110 may send the message part and enables DRX operation (570). If a NACKis received on the AICH, the WTRU 110 may enable DRX operation (580).This DRX operation may remain enabled until a RACH access procedure isreinitiated (i.e. after backoff timer expires and a persistency testpasses). Alternatively, the WTRU 110 may be configured to remain in CRXoperation until a positive ACK is received or until the WTRU 110 hasexceeded the number of retries. If the WTRU 110 has no uplink data totransmit, the WTRU 110 may be configured to remain in DRX operation.

Alternatively, the WTRU 110 may be configured to enable DRX operationafter the expiration of a timer (Tx) after the message has beentransmitted over the RACH.

Alternatively, the WTRU 110 may be configured to enable DRX operation assoon as the message has been transmitted over the RACH.

In yet another alternative, the WTRU 110 may be configured to disableDRX operation when an RRC message is transmitted over RACH and aresponse from the UTRAN is expected. The RRC message may include a CELLUPDATE message or an RRC Connection Request message. Upon reception ofthe response the WTRU 110 may be configured to enable DRX operation.

FIG. 6 shows an example DRX timing period for a WTRU during a RACHprocedure. A RACH transmission may “override” the DRX patterns in termsof downlink reception. The WTRU may be configured to receive downlinkchannels for a predetermined period of time (Tp-a) following thetransmission of a RACH preamble, even if DRX is enabled and according tothe DRX pattern, the WTRU 110 would otherwise not be scheduled for alistening period. The WTRU 110 may be configured to monitor the downlinkTp-a after sending the preamble in order to ensure that it maysuccessfully receive the AICH, where Tp-a is the preamble to acquisitionindication (AI) distance. The WTRU 110 may further be configured to wakeup to monitor the downlink channel for one access slot even if it fallsin the DRX period.

The options described in this embodiment may also be applicable to aWTRU 110 that uses the E-DCH in the CELL_FACH state and Idle mode foruplink transmission, wherein the options described are applicable untilan acknowledgement is received and/or resources are assigned for theWTRU. When the WTRU 110 starts uplink transmission using E-DCH inCELL_FACH the WTRU 110 continues with CRX operation until the resourcesare released.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

1-16. (canceled)
 17. A wireless transmit/receive unit (WTRU) comprising:a processor configured to: determine that the WTRU has a high-speeddownlink shared channel (HS-DSCH) radio network temporary identifier(H-RNTI); enable DRX operation in response to the determination that theWTRU has the H-RNTI; disable discontinuous reception (DRX) operation inresponse to a release of the H-RNTI, wherein being configured to disableDRX operation comprises being configured to start continuous receptionoperation in the WTRU; receive an E-DCH resource; release the E-DCHresource; start a timer, wherein being configured to start the timer isassociated with the release of the E-DCH resource; and enable DRXoperation in response to expiration of the timer.
 18. The WTRU of claim17, wherein the processor is further configured to receive an H-RNTIassociated with a new cell.
 19. The WTRU of claim 18, wherein theprocessor is further configured to reenable DRX operation in response toa determination that the WTRU has the H-RNTI associated with the newcell.
 20. The WTRU of claim 17, wherein to perform the cell reselectionthe processor is further configured to: transmit a CELL UPDATE messageassociated with performance of the cell reselection; and receive a CELLUPDATE CONFIRM message that indicates that the cell reselection issuccessful.
 21. The WTRU of claim 17, wherein the processor is furtherconfigured to determine that the WTRU is in a CELL_FACH state when theWTRU has the H-RNTI.
 22. The WTRU of claim 17, wherein the processor isfurther configured to perform cell reselection, and wherein the releaseof the H-RNTI is associated with the cell reselection.
 23. A methodcomprising: determining that the WTRU has a high-speed downlink sharedchannel (HS-DSCH) radio network temporary identifier (H-RNTI); enablingDRX operation in response to the determination that the WTRU has theH-RNTI; performing cell reselection and releasing the H-RNTI; disablingdiscontinuous reception (DRX) operation in response to the release ofthe H-RNTI, wherein disabling DRX operation comprises startingcontinuous reception operation in the WTRU; receiving an E-DCH resource;releasing the E-DCH resource; starting a timer, wherein the starting ofthe timer is associated with the releasing of the E-DCH resource; andenabling DRX operation in response to expiration of the timer.
 24. Themethod of claim 23, further comprising receiving an H-RNTI associatedwith a new cell.
 25. The method of claim 24, further comprisingreenabling DRX operation in response to a determination that the WTRUhas the H-RNTI associated with the new cell.
 26. The method of claim 23,further comprising: transmitting a CELL UPDATE message associated withperformance of the cell reselection; and receiving a CELL UPDATE CONFIRMmessage that indicates that the cell reselection is successful.
 27. Themethod of claim 23, further comprising determining that the WTRU is in aCELL_FACH state when the WTRU has the H-RNTI.